Partially revert CI triggering improvements

This commit partially reverts changes from elastic#4836.

Reson behind this is that the selected CI pipelines are defined as
required checks for PR and if the pipeline is not triggered then PR's
that change only files under the ignored list will not be able to get
merged.

Signed-off-by: Alexandros Sapranidis <alexandros@elastic.co>

Author: alexsapran

.buildkite/pull-requests.json

@@ -13,7 +13,7 @@
             "always_trigger_comment_regex": "^(?:(?:buildkite\\W+)?(?:build|test)\\W+(?:this|it))|^/test$",
             "skip_ci_labels": [ "skip-ci" ],
             "skip_target_branches": [ ],
-            "skip_ci_on_only_changed": [ "^.ci/", "^.github/", "^changelog", "^docs/", "\\.md$", "^docker-compose.yml", "^.pre-commit-config.yaml", "skaffold.yaml", "^Dockerfile.skaffold", "^Dockerfile"],
+            "skip_ci_on_only_changed": [ "^.ci/", "^changelog", "^docs/", "\\.md$", "^docker-compose.yml", "^.pre-commit-config.yaml", "skaffold.yaml", "^Dockerfile.skaffold", "^Dockerfile"],
             "always_require_ci_on_changed": [ ]
         },
         {
@@ -30,7 +30,7 @@
             "always_trigger_comment_regex": "^(?:(?:buildkite\\W+)?(?:build|test)\\W+(?:extended))|^/test extended$",
             "skip_ci_labels": [ "skip-ci", "skip-it" ],
             "skip_target_branches": [ ],
-            "skip_ci_on_only_changed": [ "^.ci/", "^.github/", "^changelog", "^docs/", "\\.md$", "^sonar-project.properties", "^docker-compose.yml", "^.pre-commit-config.yaml", "skaffold.yaml", "^Dockerfile.skaffold", "^Dockerfile"],
+            "skip_ci_on_only_changed": [ "^.ci/", "^changelog", "^docs/", "\\.md$", "^sonar-project.properties", "^docker-compose.yml", "^.pre-commit-config.yaml", "skaffold.yaml", "^Dockerfile.skaffold", "^Dockerfile"],
             "always_require_ci_on_changed": [ ]
         },
         {